I just tested your sign-up link and was able to join your program without any trouble. However, when I picked you from the Select Merchant menu in my Affiliate Admin and clicked Get Affiliate Code, I could only obtain a Common Hop Link for your program, since your account currently has no products and thus no product-specific affiliate links set up.
Note that if you ever deleted yourself or other affiliates from your affiliate program, those accounts are effectively banned from re-joining your program. That could explain why those users may not be finding you in their Affiliate Admin's Select Merchant menu after they click your sign-up link.
You can un-ban and reinstate those affiliates by going to your Seller Admin > View/Edit Affiliates, then enter their Affiliate ID number in the space provided. Since you're unable to join your own program, start by reinstating your own ID (46036) and then proceed with other affiliate IDs who want to rejoin (they can find their ID clearly displayed in their Affiliate Admin).